One of the most traditional and common technologies that involves detection and classification of volatile organic compounds in gas phase is an electronic nose or an electronic tongue for liquid sensing. The electronic nose is a device that combines a chemical-sensing and pattern-recognition systems; in nature it can in principle be the sensing organ of an animal like a nose of a bomb-sniffing dog. Conventional approaches to chemical sensors arrays have traditionally made use of a “lock-and-key” design, wherein a specific receptor is synthesized in order to strongly and highly selectively bind the analyte of interest. Nevertheless, the traditionally applied electronic nose technique is expensive and has certain limitations due to detection problems at low analyte concentrations, temperature and humidity requirements. Furthermore, the technical equipment can be rather heavy and difficult to move into new locations where detection is required.
Sensor arrays, in particular colorimetric sensor arrays, which involve an artificial nose having an array of at least a first dye and a second dye in combination and having a distinct spectral response to an analyte are well known in the prior art. Typical examples of sensor arrays comprising at least two different chemo-selective dyes, where the dyes are from the group of porphyrin, chlorin, chlorophyll, phthalocyanine, or salen, in particular metalated or non-metalated porphyrines and derivatives thereof are known for example from U.S. Pat. Nos. 6,495,102, 6,368,558 and 7,261,857 in which the sensor arrays are particular useful for detecting metal ligating vapors. US2000050839 describes an apparatus and method including a colorimetric array comprising porphyrinogen dyes to detect lung cancer via exhaled breath. US20080199904 describes an apparatus and method including a colorimetric array comprising porphyrinogen dyes to detect and identifying microorganisms. WO2010028057 describes a colorimetric array comprising of nanoporous pigments based on porphyrinogen dyes. A sensor device comprising porphyrinogen derivatives having binding affinity for explosives is known from WO2007132430.
The chemical diversity of the metalated or non-metalated porphyrines and the derivatives thereof described above is relatively limited and only well suited for the detection of metal ligating analytes. The porphyrinogen derivatives having high binding affinity for explosives suffers from a strong cross-reactivity with other electron-deficient guests like chloride ions (JACS, 2004, 126, 16296-16297) (JACS, 2006, 128, 2444-2451). Furthermore, the described sensor molecules are relatively complex molecules with a limited chemical diversity.
Also operational constraints for example environmental changes such as temperature, humidity and large number of interferants giving rise to false positives and false negatives due to too low sensitivity makes it highly desirable with a new class of sensor molecules to provide an improved sensor array in particular a more efficient and/or reliable sensor array.